Some examples that show why a wide gamut monitor matters:

EDIT: note that these are all posted in ProphotoRGB (a non color-managed browser may make them look faded out and odd which is not what I'm trying to get at, that is a totally different issue)

If you view some of these in regular gamut they will look HORRENDOUS! No detail, clipped, weird colors, awful. Viewed on a wide gamut monitor the colors tones are detailed, no clipping, so rich, different shades entirely in some cases, vastly different looking.